Commercially and clinically, silicone hydrogel contact lenses are a popular alternative to conventional hydrogel contact lenses (i.e., hydrogel contact lenses that do not contain silicone or silicone-containing ingredients). The presence of siloxanes in silicone hydrogel contact lens formulations is believed to affect the properties of silicone hydrogel contact lenses obtained therefrom. For example, it is believed that the presence of a polymerizable siloxane component in a polymerizable composition used to form a contact lens results in a relatively higher oxygen permeability compared to a conventional hydrogel contact lens without a polymerizable siloxane component. In addition, it is believed that the presence of a polymerizable siloxane component increases the likelihood of hydrophobic domains being present on the lens surface of a silicone hydrogel contact lens as compared to a conventional hydrogel contact lens without a polymerizable siloxane component. The first generation of silicone hydrogel contact lenses provided high levels of oxygen, even though the wettability of the lenses tended to be lower than might be desired. Techniques have been developed to overcome the hydrophobicity issues of silicone hydrogel contact lens surfaces. Based on the popularity of silicone hydrogel contact lenses, there continues to be a need for new silicone hydrogel contact lenses that are ophthalmically compatible, such as new silicone hydrogel contact lenses having higher water contents.
Some documents describing silicone hydrogel contact lenses include: U.S. Pat. No. 4,711,943, U.S. Pat. No. 5,712,327, U.S. Pat. No. 5,760,100, U.S. Pat. No. 7,825,170, U.S. Pat. No. 6,867,245, US20060063852, US20070296914, U.S. Pat. No. 7,572,841, US20090299022, US20090234089, and US20100249356, each of which is incorporated in its entirety by reference herein.